Bronze whaler - more than meets the eye!

If you’re surfing the North Island beaches this summer don’t
be surprised if the sleek bronze body next to you riding the
waves is that of a Bronze Whaler shark.

“At 3 metres long, Bronze Whaler sharks can get quite large,”
says NIWA Principal Scientist, Dr Malcolm Francis. On average
they are 1.5–2.5 metres in length. The Bronze Whaler is one
of the largest reef shark species, and one of the most abundant
large shark species in New Zealand coastal waters. It is also
the species most likely to be encountered by divers around New
Zealand, from Cape Reinga to Cook Strait.

They live in shallow coastal waters during the summer – reefs,
bays, estuaries and surf beaches, and in winter are found further
offshore.

The Bronze Whaler, as the name suggests, is bronze to grey-brown
in colour. If you’re diving and they are above you, their underbellies
are cream in colour. The first dorsal fin is large relative to
the second, and the tail's upper lobe is 2–3 times longer than
the lower lobe.

Their skin is thick and leathery to touch. They have denticles,
which are like small teeth, embedded in the skin. These channel
water-flow over their bodies, for easily slipping through the
water.

Their teeth are designed for grasping small prey, such as slippery
fish and squid, rather than for cutting big hunks of flesh. They
have 63-65 functional teeth, and these are about 20-30 mm in
height.

Bronze Whalers have an incredibly good sensory system and they
are very adept at learning about, and exploiting their environment.
“They learn well in choice experiments,” says Malcolm Francis,
and they know where to go to find prey at certain times of the
year.

They are not normally aggressive towards humans, although spear
fishers have been bitten by excited sharks. However, they are
opportunistic eaters which mean that they will eat live or dead
animal matter. They mainly eat small schooling fishes such as
kahawai. “Sharks have a lateral line sense which can detect
vibrations in the water. If you're in the water and see a shark,
don't splash about and don't panic. It™s highly unlikely
that they will bite you," says Malcolm Francis.

Their eyesight is probably limited only by the visibility of
the water. They may be able to see tens of metres, as far as
humans can, under water.

“Bronze Whaler sharks occur in pairs or in small groups. Sightings
increase at this time of the year, partly because more New Zealanders
head for the beach in summer, but also because they come into
warmer waters to chase fish or give birth to their young,”
says Malcolm Francis.

SPECIES FACT FILE (see printer-friendly version on ftp for table)

*Common Name: Bronze Whaler
*MAori names: Horopekapeka, matawhA, tOiki, ngerungeru.
*Scientific name: Carcharhinus brachyurus
*Family: Carcharhinidae
*Type: Cartilaginous fish
*Size: 3 metres
*Lifespan: Perhaps 30-40 years
*Diet: They eat mainly fish – kahawai, pilchards, yellow eyed
mullet and stingray.
*Reproduction: 7-24 young born at 60-70 cm.They can be seen close
to shore, when they may be pupping. As in all sharks, the eggs
are fertilised internally; sperm are transferred to the female
by the male’s claspers.
*Things you need to know: If you’re in the water and see a
shark don’t panic – stay still and quiet until it moves away.
Don't go in the water near fishers, or where fish waste is being
discarded. Spear fishers should remove dead fish from the sea
immediately.
*Something strange: Sharks can’t swim backwards